Trustworthiness of information sources and information pedigrees

To survive, and indeed thrive, in an open heterogenous information sharing environment, an agent's ability to evaluate the trustworthiness of other agents becomes crucial. In this paper, we investigate a procedure for evaluating an agent's trustworthiness as an information source. By separating the procedure into competency analysis and sincerity analysis, we are able to deal with complicated cases involving the passing-on of information, where the same information may reach a receiver agent via different routes. In order to keep information about the source agent we use an information pedigree as a means to maintain the history of communicated information. Our evaluation of trustworthiness can be employed to drive data fusion, weighted knowledge base merging, and multiple source conflict resolution. © Springer-Verlag Berlin Heidelberg 2002

Shifting food web structure during dam removal-Disturbance and recovery during a major restoration action.

We measured food availability and diet composition of juvenile salmonids over multiple years and seasons before and during the world's largest dam removal on the Elwha River, Washington State. We conducted these measurements over three sediment-impacted sections (the estuary and two sections of the river downstream of each dam) and compared these to data collected from mainstem tributaries not directly affected by the massive amount of sediment released from the reservoirs. We found that sediment impacts from dam removal significantly reduced invertebrate prey availability, but juvenile salmon adjusted their foraging so that the amount of energy in diets was similar before and during dam removal. This general pattern was seen in both river and estuary habitats, although the mechanisms driving the change and the response differed between habitats. In the estuary, the dietary shifts were related to changes in invertebrate assemblages following a hydrological transition from brackish to freshwater caused by sediment deposition at the river's mouth. The loss of brackish invertebrate species caused fish to increase piscivory and rely on new prey sources such as plankton. In the river, energy provided to fish by Ephemeroptera, Plecoptera, and Trichoptera taxa before dam removal was replaced first by terrestrial invertebrates, and then by sediment-tolerant taxa such as Chironomidae. The results of our study are consistent with many others that have shown sharp declines in invertebrate density during dam removal. Our study further shows how those changes can move through the food web and affect fish diet composition, selectivity, and energy availability. As we move further along the dam removal response trajectory, we hypothesize that food web complexity will continue to increase as annual sediment load now approaches natural background levels, anadromous fish have recolonized the majority of the watershed between and above the former dams, and revegetation and microhabitats continue to develop in the estuary